The art of glass container manufacture is currently dominated by the so-called individual section or IS machine. Such machines include a plurality of separate or individual manufacturing sections, each of which has a multiplicity of operating mechanisms for converting one or more charges or gobs of molten glass into hollow glass containers and transferring the containers through successive stages of the machine section. In general, an IS machine system includes a glass source with a needle mechanism for controlling a stream of molten glass, a sheer mechanism for cutting the molten glass stream into individual gobs, and a gob distributor for distributing the individual gobs among the individual machine sections. Each machine section includes one or more blank molds in which a glass gob is initially formed into a parison in a blowing or pressing operation, one or more invert arms for transferring the parisons to blow molds in which the containers are blown to final form, tongs for removing the formed containers onto a deadplate, and a sweepout mechanism for transferring molded containers from the deadplate onto a cross conveyor. The conveyor receives containers from all sections of an IS machine in sequence, and conveys the containers to a loader for transfer to an annealing lehr. Operating mechanisms in each section also provide for closure of mold halves, movement of baffles and blowing nozzles, control of cooling wind, etc. U.S. Pat. No. 4,362,544 includes a background discussion of the art of both "blow and blow" and "press and blow" glassware forming processes, and also discusses an electropneumatic individual section machine adapted for use in either process.
A critical requirement in glassware forming systems of this character, both during initialization and during continuing operation, is to synchronize operation of the glassware forming machine to the sequential supply of molten glass gobs. Operation of the various machine sections is electronically synchronized by a machine reset signal. A signal may also be provided by the gob feeder mechanism, generated either by a sensor or electronically responsive to feeder control electronics. It is proposed in Canadian Patent 1,198,793 to provide a counter responsive to clock signals from the various operating mechanisms, such as the gob feeder and the machine reset signal, for measuring offset therebetween in units of machine degrees. These offsets are manually noted, and manually reset upon the initialization after shutdown. However, gob travel time from the feeder to the blank molds is relatively constant in real time, and does not vary with machine speed. Thus, setting offset times in units of machine degrees does not provide adequate synchronization as machine speed varies. Furthermore, timing adjustments are made manually rather than automatically in the noted patent.
U.S. Pat. No. 4,108,623 discloses an IS machine control system that operates in real time, as distinguished from operating in machine or section degrees as is more typical in the art. The time between gob shear and entry into the blank mold is measured by employing a first sensor for generating a signal indicative of entry of a gob into the gob distributor, and a second sensor for generating a signal indicative of entry of the gob into the blank mold. Mold operation is initiated by the sensor responsive to gob entry into the mold. There is no fixed time between shear cut and operation of the blank mold.
It is a general object of the present invention to provide a method and system for synchronizing operation of the forming machine to provision of molten glass gobs in an IS machine glassware forming system that automatically synchronize operation upon initialization of the system, and that automatically maintain such synchronization during system operation.